JP6981885B2 - Anomaly detection method and device for capacitive pressure sensor - Google Patents

Description

The present invention relates to an abnormality detection method and an apparatus of a capacitance type pressure sensor provided with a sensor element having a diaphragm structure for detecting a capacitance according to the pressure of a medium to be measured.

Conventionally, pressure sensors such as vacuum gauges used in semiconductor manufacturing equipment often employ a sensor element having a small diaphragm by using so-called MEMS (Micro Electro Mechanical Systems) technology. The main detection principle of this sensor element is to receive a pressure medium with a diaphragm and convert the displacement or stress generated in the diaphragm into some kind of signal.

For example, as a pressure sensor using this type of sensor element, the capacitance that detects the displacement of the diaphragm (diaphragm) that bends under the pressure of the medium to be measured as a change in capacitance (change in capacitance between electrodes). Type pressure sensors are widely known.

Since this capacitance type pressure sensor does not depend on the gas type, it is often used in industrial applications such as semiconductor equipment. For example, it is used to measure the pressure of gas during the manufacturing process in semiconductor manufacturing equipment, and in this application, the above-mentioned capacitive pressure sensor is called a capacitive diaphragm vacuum gauge. .. Further, the diaphragm that bends under the pressure of the medium to be measured is called a pressure-sensitive diaphragm or a sensor diaphragm (see, for example, Patent Documents 1, 2 and 3).

It is known that the main applications of this gas type-independent diaphragm vacuum meter are CVD (chemical vapor deposition), ALD (Atomic Layer Deposition), deposition such as sputtering, or etching processes using plasma in semiconductor manufacturing processes. Has been done. In the film formation process, the film deposited on the substrate and similar incomplete films, and in the etching process, the residue of the resist and the by-products generated when the substrate is etched are the chambers, pipes, and pumps. It accumulates more or less inside and causes various troubles.

Among them, the deposition of the above substances on a diaphragm vacuum gauge that measures and controls the pressure of gas in the process, especially on the diaphragm that senses pressure, causes the diaphragm to bend independently of the measured pressure due to the stress. Will result in a shift of zeros that does not show zero when drawn to vacuum.

Further, although the thickness of the diaphragm is apparently increased depending on the quality of the deposited film, the deflection becomes small even when the same pressure is applied, which causes a decrease in pressure sensitivity. In addition, if the deposited material is viscous, the movement of the diaphragm may be delayed, which is directly linked to the delay in the sensor response.

As a matter of course, the shift of the zero point of the output and the change of the pressure sensitivity due to the accumulation inside the vacuum gauge may have a great influence on the quality of film formation and etching with this as the main control parameter. Are known.

Therefore, in the past, when the zero point shifts from a certain specified value, the following adjustments are made.
Adjustment (1): The entire device is evacuated to adjust the zero point.
Adjustment (2): If the vacuum cannot be drawn by adjustment (1), remove the vacuum gauge from the device and recalibrate.

Japanese Unexamined Patent Publication No. 2010-236949 Japanese Unexamined Patent Publication No. 2000-105164 Japanese Unexamined Patent Publication No. 2006-3234 Japanese Unexamined Patent Publication No. 2015-184064

However, the pressure for pulling out to the vacuum depends on the suction capacity of the pump, the arrangement of the pipes, and the like, and the degree of vacuum may actually deteriorate and there may be no problem with the vacuum gauge. Therefore, the above-mentioned methods of adjustment (1) and (2) cause the following problems.

Problem of adjustment (1): Unnecessary zero point adjustment is performed on the correct vacuum gauge, and rather the pressure measurement is incorrect.
Problem of adjustment (2): If the vacuum gauge is removed from the device, the device will stop for a long time due to unnecessary zero point adjustment.

Reducing the number of such adjustments as much as possible helps to improve the operating rate of the equipment, but when the pressure is actually changing (when zero point adjustment is not necessary) and when there is a shift due to deposits, etc. It is very difficult to distinguish from (when zero adjustment is required).

In Patent Document 4, a step portion is provided between the peripheral portion and the central portion of the surface of the diaphragm on the pressure introduction chamber side, and the central portion side region (thin region) and the peripheral portion side are provided with this step portion as a boundary. The pedestal plate is divided into regions (thick regions), and the pedestal plate is provided with a plurality of pressure introduction holes so that the openings are located near the stepped portion of the diaphragm (region on the peripheral edge side) to suppress the zero shift. I am doing it. However, this method is limited to suppressing the zero shift.

The present invention has been made to solve such a problem, and an object thereof is to distinguish between an output change due to pressure and an output change other than pressure due to deposits, etc., and reduce unnecessary zero point adjustment. It is an object of the present invention to provide a method and an apparatus for detecting an abnormality of a capacitive pressure sensor.

In order to achieve such an object, the present invention provides a plurality of electrode pairs (D1, D2) in which the capacitance between the electrodes changes according to the displacement of the diaphragm (101) that bends according to the pressure of the medium to be measured. It is an abnormality detection method of the capacitance type pressure sensor for detecting the abnormality of the capacitance type pressure sensor (100) provided, and is a method of detecting the capacitance (Cx, Cr) of a plurality of electrode pairs at the time of vacuuming the test medium. By comparing the index calculation step (S201) for calculating the abnormality detection index (α) from the change, the abnormality detection index calculated by the index calculation step, and the reference value (αref) indicating the index at normal times. It is characterized by including a state determination step (S202) for determining whether or not the diaphragm is bent due to a factor other than pressure.

In the present invention, an abnormality detection index is calculated from a change in the capacitance of a plurality of electrode pairs when the measured medium is evacuated, and the calculated abnormality detection index is compared with a reference value indicating the index at normal times. By doing so, it is determined whether or not the diaphragm is bent due to a factor other than pressure. For example, when the electrode pair forming the pressure-sensitive capacitance Cx in the central portion of the diaphragm is the first electrode pair and the electrode pair forming the reference capacitance Cr in the outer peripheral portion of the diaphragm is the second electrode pair, the pressure-sensitive capacitance Cx The ratio ΔCx / ΔCr between the change ΔCx and the change ΔCr of the reference capacitance Cr is calculated as the index α for abnormality detection, and the calculated index α for abnormality detection is compared with the reference value αref indicating the index at normal times. Determines whether or not the diaphragm is bent due to factors other than pressure.

This makes it possible to distinguish between output changes due to pressure and output changes other than pressure due to deposits, etc., and to reduce unnecessary zero point adjustment.

An electrode pair forming the deposition sensing capacity Cd is provided at a position corresponding to the inlet of the medium to be measured into the diaphragm, and this electrode pair is used as the first electrode pair, and the change ΔCd of the deposition sensing capacity Cd and the reference capacity Cr are used. By calculating the ratio ΔCd / ΔCr with the change ΔCr as the index β for abnormality detection and comparing the calculated index β for abnormality detection with the reference value βref indicating the index at normal times, the diaphragm has a pressure other than the pressure. It may be determined whether or not the bending is caused by a factor.

Further, an electrode pair forming a deposit sensing capacity Cd is provided at a position corresponding to the introduction port of the medium to be measured into the diaphragm, and this electrode pair is used as a third electrode pair, and the change ΔCx of the pressure-sensitive capacity Cx and the reference capacity Cr are used. The ratio ΔCx / ΔCr to the change ΔCr and the change ΔCd of the deposition sensing capacity Cd and the ratio ΔCd / ΔCr to the change ΔCr of the reference capacity Cr were calculated as the abnormality detection indexes α and β, and the calculated abnormality detection index α , Β may be compared with the reference values αref and βref indicating the index at normal times to determine whether or not the diaphragm is bent due to a factor other than pressure.

In the above description, as an example, the components on the drawing corresponding to the components of the invention are shown by reference numerals in parentheses.

As described above, according to the present invention, an abnormality detection index is calculated from the change in the capacitance of a plurality of electrode pairs when the test medium is evacuated, and the calculated abnormality detection index and the normal time index are calculated. By comparing with the reference value indicating, it is determined whether or not the diaphragm is bent due to factors other than pressure, so the output change due to pressure and the output change other than pressure due to sediment etc. can be determined. It is possible to distinguish and reduce unnecessary zero point adjustment.

FIG. 1 is a diagram showing a deflection curve of a circular diaphragm having a uniform thickness when pressure is applied. FIG. 2 is a diagram showing a configuration of a main part of an example of a capacitance type pressure sensor to which the present invention is applied. FIG. 3 is a diagram showing the arrangement of the pressure-sensitive side fixed electrode and the reference side fixed electrode formed on the sensor pedestal in this capacitance type pressure sensor together with the positions of the pressure introduction holes. FIG. 4 is a diagram showing a state in which a deposit film is formed on the diaphragm of the capacitance type pressure sensor. FIG. 5 is a diagram showing a calculation result (1/4 model) in which the central portion of the diaphragm of the capacitance type pressure sensor is greatly deflected by the deposition film when the deposition as shown in FIG. 4 occurs. FIG. 6 is a diagram showing the arrangement of the pressure-sensitive side electrode pair and the reference side electrode pair in this capacitance type pressure sensor. FIG. 7 is a diagram showing calculated values of the pressure-sensitive capacity Cx and the reference capacity Cr with respect to the applied pressure. FIG. 8 is a diagram showing the calculated value of Cx—Cr with respect to the applied pressure. In FIG. 9, the ratio ΔCx / ΔCr between the change ΔCx of the pressure sensitive capacity Cx and the change ΔCr of the reference capacity Cr is the deposited film in the region of 10 Pa or less corresponding to 10% FS (full scale) when 100 Pa is set to full scale. It is a figure explaining that there is a big difference between the state where the film is formed and the state where the film is not formed. FIG. 10 is a block diagram showing a configuration of a main part of an abnormality detection device for a capacitance type pressure sensor according to the first embodiment of the present invention. FIG. 11 is a flowchart showing a pre-operation process in the abnormality detection device of the first embodiment. FIG. 12 is a flowchart showing a process during operation in the abnormality detection device of the first embodiment. FIG. 13 is a diagram showing a configuration of a main part of another example of a capacitive pressure sensor to which the present invention is applied. FIG. 14 is a diagram showing the arrangement of the pressure-sensitive side fixed electrode and the reference side fixed electrode formed on the sensor pedestal in this capacitance type pressure sensor together with the positions of the pressure introduction holes. FIG. 15 is a diagram showing a state in which a deposit film is formed on the diaphragm of the capacitance type pressure sensor. FIG. 16 shows a calculation result (1 /) in which the portion corresponding to the pressure introduction hole located in the region on the peripheral edge side of the diaphragm of the capacitive pressure sensor is greatly bent when the deposition as shown in FIG. 15 occurs. It is a figure which shows 4 models). FIG. 17 is a diagram showing the arrangement of the pressure sensitive side electrode pair, the reference side electrode pair, and the deposition sensing electrode pair in this capacitance type pressure sensor. FIG. 18 is a block diagram showing a configuration of a main part of an abnormality detection device for a capacitance type pressure sensor according to the second embodiment of the present invention. FIG. 19 is a flowchart showing a process before operation in the abnormality detection device of the second embodiment. FIG. 20 is a flowchart showing a process during operation in the abnormality detection device of the second embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First, the principle of the present invention will be described before going into the description of the embodiments.

[Principle of invention]
The inventor has found that the shape of the deflection differs between the deflection of the diaphragm due to pressure (appropriate deflection) and the deflection of the diaphragm due to factors other than pressure such as deposits (inappropriate deflection). Normally, the shape of the sensor diaphragm when it receives pressure is formulated as the deflection w (r) of the peripherally fixed disk that has received uniform pressure, as shown by the following equation (1), and the pressure p. The deflection w when is added is a quartic function of the distance r from the center of the diaphragm (see FIG. 1).

In many cases, the output of a capacitive pressure sensor has a pressure-sensitive capacitance Cx and a reference capacitance Cr arranged in the cavity to suppress thermal characteristics derived from thermal expansion and contraction, reduce electrical noise, and permittivity in the cavity. The difference Cx-Cr is used as an output (sensor output) for the purpose of removing the influence of the change in the rate.

FIG. 2 shows the configuration of a main part of an example of a capacitive pressure sensor to which the present invention is applied. The capacitance type pressure sensor 100 includes a diaphragm component 103 having a diaphragm 101 that is displaced according to the pressure of the medium to be measured, and a diaphragm support portion 102 that supports a peripheral portion of the diaphragm 101, and a diaphragm support portion 102. A pedestal plate that is joined to the sensor pedestal 105 that forms a reference vacuum chamber (cavity) 104 together with the diaphragm 101 and a pedestal plate that is joined to the side opposite to the sensor pedestal 105 of the diaphragm support 102 and forms a pressure introduction chamber 106 together with the diaphragm 101. It is equipped with 107.

In the capacitance type pressure sensor 100, a pressure-sensitive fixed electrode 108 and a reference-side fixed electrode 109 are formed on the surface of the sensor pedestal 105 on the reference vacuum chamber 104 side, and on the surface of the diaphragm 101 on the reference vacuum chamber 104 side. The pressure-sensitive side movable electrode 110 and the reference side movable electrode 111 are formed. The pressure-sensitive fixed electrode 108 and the pressure-sensitive movable electrode 110 are provided in the central portion of the diaphragm 101 so as to face each other, and the reference-side fixed electrode 109 and the reference-side movable electrode 111 of the diaphragm 101 face each other. It is provided on the outer peripheral portion. Further, the pedestal plate 107 is formed with a pressure introduction hole 112 in the central portion (a portion located at the center of the diaphragm 101) of the plate.

FIG. 3 shows the arrangement of the pressure-sensitive fixed electrode 108 and the reference-side fixed electrode 109 formed on the sensor pedestal 105 together with the positions of the pressure introduction holes 112. The pressure-sensitive fixed electrode 108 having a substantially circular shape in a plan view is formed on the surface of the sensor pedestal 105 on the reference vacuum chamber 104 side so that the center thereof substantially coincides with the center of the diaphragm 101. The reference side fixed electrode 109 having a substantially arc shape in a plan view is formed on the surface of the sensor pedestal 105 on the reference vacuum chamber 104 side so as to be arranged substantially concentrically on the outside of the pressure sensitive side fixed electrode 108. The pressure-sensitive fixed electrode 108 is electrically connected to a signal processing device (not shown) outside the sensor via a wiring 113 formed on the sensor pedestal 105. Similarly, the reference-side fixed electrode 109 is electrically connected to the signal processing device via the wiring 114 formed on the sensor pedestal 105.

The configuration of the movable electrode on the diaphragm 101 side is the same as that of the fixed electrode. That is, the pressure-sensitive movable electrode 110 having a substantially circular shape in a plan view is formed on the surface of the diaphragm 101 on the reference vacuum chamber 104 side so as to face the pressure-sensitive fixed electrode 108. The center of the pressure-sensitive movable electrode 110 substantially coincides with the center of the diaphragm 101. The reference side movable electrode 111 having a substantially arc shape in a plan view is formed on the surface of the diaphragm 101 on the reference vacuum chamber 104 side so as to face the reference side fixed electrode 109. The reference-side movable electrode 111 is arranged substantially concentrically on the outside of the pressure-sensitive side movable electrode 110. The pressure-sensitive movable electrode 110 is electrically connected to a signal processing device outside the sensor via wiring (not shown) formed in the diaphragm 101. Similarly, the reference-side movable electrode 111 is electrically connected to the signal processing device via a wiring (not shown) formed in the diaphragm 101.

The capacitance composed of the pressure-sensitive fixed electrode 108 and the pressure-sensitive movable electrode 110 is highly sensitive to pressure and serves to measure pressure. The capacitance composed of the reference-side fixed electrode 109 and the reference-side movable electrode 111 has low sensitivity to pressure and serves to correct the dielectric constant between the electrodes. Hereinafter, the electrode pair of the pressure-sensitive fixed electrode 108 and the pressure-sensitive movable electrode 110 is referred to as a pressure-sensitive electrode pair D1, and the electrode pair of the reference-side fixed electrode 109 and the reference-side movable electrode 111 is referred to as a reference-side electrode pair D2. The pressure-sensitive electrode pair D1 forms a pressure-sensitive capacitance Cx in the central portion of the diaphragm 101, and the reference-side electrode pair D2 forms a reference capacitance Cr in the outer peripheral portion of the diaphragm 101.

In the capacitance type pressure sensor 100, the medium to be measured is introduced into the pressure introduction chamber 106 through the pressure introduction hole 112 from the direction intersecting the surface of the diaphragm 101 (in this example, the direction perpendicular to the surface of the diaphragm 101). Then, the diaphragm 101 is deformed according to the pressure of the medium to be measured. When the diaphragm 101 is deformed, the distance between the sensor pedestal 105 and the diaphragm 101 (height of the reference vacuum chamber 104) changes, and the pressure-sensitive capacity Cx formed by the pressure-sensitive electrode pair D1 and the reference capacity formed by the reference-side electrode pair D2. Cr changes. A signal processing device (not shown) calculates a sensor output as Cx-Cr, and converts this sensor output (capacity value) into a pressure value.

The base material constituting the capacitance type pressure sensor 100, that is, the diaphragm component 103, the sensor pedestal 105, and the pedestal plate 107 are heat resistant such as sapphire, alumina ceramic, glass, silicon, nickel alloy, and stainless steel. It is composed of a corrosion-resistant material.

In this capacitance type pressure sensor 100, the pressure sensitive capacitance Cx and the reference capacitance Cr are given by the following equations (2-1) and (2-2).

In the equations (2-1) and (2-2), the deflection w (r) due to pressure is strictly defined as the equation (1) above, and the ratio of the change in each capacitance due to pressure (pressure sensitive capacitance Cx). Ratio of change ΔCx to change ΔCr of reference capacitance Cr) ΔCx / ΔCr has a substantially constant value in a range where the deflection w to be adjusted at the zero point is small.

On the other hand, shifts due to factors other than pressure, especially shifts due to membrane deposition during the process, do not always occur at this ratio. For example, as shown in FIG. 4, the thickness of the film (deposited film) 115 deposited on the diaphragm 101 changes depending on the position of the pressure introduction hole 112, and the bending w generated by the change also changes in various ways.

That is, as shown in FIG. 4, if the film 115 is thickly deposited just below the pressure introduction hole 112 (the central portion of the diaphragm 101), that portion is greatly flexed by the film stress (see FIG. 5). The rate of change in Cr (ΔCx / ΔCr) is expected to take a different value than when pressure is applied.

Therefore, the inventor has an appropriate deflection shape based on the pattern of signals from a plurality of electrode pairs in which the capacitance between the electrodes changes according to the displacement of the diaphragm that bends according to the pressure of the medium to be measured. By distinguishing (or separating) the signal due to the above and the signal due to the improper deflection shape, it was conceived that unnecessary zero point adjustment can be reduced.

Specifically, an anomaly detection index is calculated from the change in the capacitance of a plurality of electrode pairs when the test medium is evacuated, and the calculated anomaly detection index is compared with the reference value indicating the index at normal times. By doing so, I came up with the idea that it is possible to determine whether or not the diaphragm is bent due to factors other than pressure.

[Outline of Embodiment]
In the embodiment, the following functions are provided as basic requirements.
1. 1. Place multiple capacities in the cavity.
2. 2. It is equipped with a mechanism that can measure and store signals based on the deflection shape of the diaphragm, as well as the output by simply increasing or decreasing the capacitance value.
3. 3. The "signal pattern from a plurality of pairs of electrodes (reference pattern)" based on the bending shape (appropriate bending) of the diaphragm due to the application of each pressure is measured and stored in advance. (Example: For a disk of uniform thickness, the deflection due to pressure application is a quartic function of thickness)
4. The "signal pattern from multiple pairs of electrodes (actual measurement pattern)" is acquired when applying an actual process in which a zero shift is expected due to factors other than pressure, such as deposition on the diaphragm.
5. Based on the reference pattern and the measured pattern, the signal due to the appropriate deflection shape and the signal due to the inappropriate deflection shape are discriminated, and the suitability / unsuitability is notified.

Hereinafter, as an embodiment, a capacitance type pressure sensor (capacitance type pressure sensor 100 having the structure shown in FIG. 2) in which a pressure introduction hole is provided in the central portion of the surface of the diaphragm, and a diaphragm. Capacitance type pressure sensor (capacitance type pressure sensor 100'with the structure shown in FIG. 13 to be described later) having a plurality of pressure introduction holes dispersed in a position avoiding the central part of the surface. As an example, as the first embodiment of the application example to the capacitance type pressure sensor 100 having the structure shown in FIG. 2, the application example to the capacitance type pressure sensor 100'with the structure shown in FIG. 13 is carried out. The second embodiment will be described.

[Embodiment 1: Example of signal processing using ordinary Cx and Cr]
In the capacitance type pressure sensor 100 having the structure shown in FIG. 2, when the following dimensions and material parameters are given as specific examples, the arrangement of the pressure-sensitive side electrode pair D1 and the reference side electrode pair D2 is shown in FIG. It has a similar shape.

[Dimensions, material parameters]
Young's modulus of diaphragm E: 350 GPa, Poisson's ratio of diaphragm: 0.25, diaphragm thickness h: 50 um, diaphragm radius a: 5 mm, cavity depth d ₀ : 2 um, vacuum permittivity: 8.854e-12F / m, Cx diameter : 2.005 mm, Cr inner diameter: 3.997 mm, Cr outer diameter: 4.471 mm.

In this case, when the pressure-sensitive capacitance Cx and the reference capacitance Cr with respect to the applied pressure are calculated based on the above-mentioned equations (2-1) and (2-2), the values of Cx and Cr as shown in FIG. 7 are obtained. Be done. Further, the value of Cx−Cr as shown in FIG. 8 can be obtained.

For example, assuming that 100 Pa is the full scale of the sensor, whether or not to adjust the zero point becomes a problem in the range of 0 to 10 Pa of about 10% FS (full scale). Now, for each capacitance of Cx and Cr, the difference between the capacitance value when each pressure is applied and the capacitance value when no pressure is applied, that is, the change ΔCx of the pressure-sensitive capacitance Cx and the change ΔCr of the reference capacitance Cr are taken. When the ratio ΔCx / ΔCr is plotted against the pressure, the characteristic I shown in FIG. 9 is obtained.

FIG. 9 also shows the ratio ΔCx / ΔCr of the difference between the capacitance values of the simulation results when the pressure is applied in the state where the deposition film 115 is formed on the diaphragm 101 (FIG. 4) as the characteristics II and III. The characteristic II shows the case where the diameter of the pressure introduction hole 112 is 1.0 mm, and the characteristic III shows the case where the diameter of the pressure introduction hole 112 is 2.0 mm. Note that FIG. 9 also shows the case where the capacitance type pressure sensor 100'with the structure shown in FIG. 13 has four pressure introduction holes 112 as the characteristic IV.

From this result, the ratio ΔCx / ΔCr is almost constant at 10 Pa or less, which corresponds to 10% FS, and the pressure dependence is small. It can be seen that the value is significantly different from that of (without objects). Therefore, if this ratio ΔCx / ΔCr is a signal based on the bending shape of the diaphragm 101 due to pressure, it is possible to distinguish the zero shift due to bending due to a factor other than pressure.

Specifically, for example, as shown in FIG. 9, the normal ratio ΔCx / ΔCr is set as the reference value αref, the range of ± th (the range indicated by the dotted line) is defined with respect to this reference value αref, and the zero point of the vacuum gauge is set. If the ratio α = ΔCx / ΔCr when the pump is pulled off (during vacuum pulling) is not within the range of αref ± th when the pump is displaced, it can be considered that a shift due to deposits or the like has occurred. That is, it can be considered that the diaphragm 101 is bent due to a factor other than the pressure.

FIG. 10 is a block diagram showing a configuration of a main part of the abnormality detection device 200 of the capacitance type pressure sensor according to the first embodiment of the present invention. The abnormality detection device 200 is realized by hardware including a processor and a storage device, and a program that realizes various functions in cooperation with these hardware, and is realized by a sensor unit 1, a capacitance output unit 2, and characteristic measurement. A unit 3, a reference value storage unit 4, a threshold value storage unit 5, a state determination unit 6, and an alarm output unit 7 are provided.

In this abnormality detection device 200, the sensor unit 1 is a pressure-sensitive side electrode pair D1 and a reference side electrode pair D2 in the capacitance type pressure sensor 100 shown in FIG. Further, the abnormality detection device 200 is incorporated in a signal processing device attached to the capacitance type pressure sensor 100.

Hereinafter, with reference to the flowcharts shown in FIGS. 11 and 12, the functions of the capacity output unit 2, the characteristic measurement unit 3, the reference value storage unit 4, the threshold value storage unit 5, the state determination unit 6, and the alarm output unit 7 are described. I will explain it with the operation.

In this embodiment, before the capacitance type pressure sensor 100 is shipped (before operation), when the sensor is characterized, the sensor output Cx-Cr is not only stored but also used as an index for detecting an abnormality. The value of the ratio ΔCx / ΔCr between the change ΔCx of the pressure-sensitive capacitance Cx and the change ΔCr of the reference capacitance Cr when the pressure is applied in the measurement range is also recorded.

Specifically, with the pressure in the measurement range applied, the signal emitted from the sensor unit 1 is converted into the pressure-sensitive capacity Cx and the reference capacity Cr by the capacity output unit 2, and the pressure-sensitive capacity is converted by the characteristic measurement unit 3. The ratio ΔCx / ΔCr between the change ΔCx of Cx and the change ΔCr of the reference capacitance Cr is calculated as the ratio ΔCx / ΔCr in the normal state (FIG. 11: step S101), and the calculated ratio ΔCx / ΔCr in the normal state is the reference value αref. Is stored in the reference value storage unit 4 (step S102).

Next, when the shift of the sensor occurs through the actual process and it is judged whether it is due to the deterioration of the pressure (during operation), it is emitted from the sensor unit 1 in a state of being evacuated by pulling off the pump. The signal is converted into the pressure-sensitive capacitance Cx and the reference capacitance Cr by the capacitance output unit 2, and the ratio ΔCx / ΔCr of the change ΔCx of the pressure-sensitive capacitance Cx and the change ΔCr of the reference capacitance Cr is used as an index for abnormality detection in the characteristic measurement unit 3. Calculated as α (FIG. 12: step S201). The abnormality detection index α measured by the characteristic measurement unit 3 is sent to the state determination unit 6.

The state determination unit 6 is specifically stored in the threshold value storage unit 5 by comparing the index α for detecting an abnormality from the characteristic measurement unit 3 with the reference value αref stored in the reference value storage unit 4. By reading out the threshold value th and confirming whether or not the abnormality detection index α is within the range of αref ± th, is the diaphragm 101 of the capacitance type pressure sensor 100 bent due to a factor other than pressure? It is determined whether or not (step S202).

In this case, the state determination unit 6 determines that the diaphragm 101 is not bent due to a factor other than the pressure when the abnormality detection index α is within the range of αref ± th (“normal” in step S202). ), When the abnormality detection index α is out of the range of αref ± th, it is determined that the diaphragm 101 is bent due to a factor other than the pressure (“abnormality” in step S202). The determination result in the state determination unit 6 is sent to the alarm output unit 7.

The alarm output unit 7 issues an alarm when a determination result indicating that the diaphragm 101 is bent due to a factor other than pressure is sent, that is, when a determination result indicating that the diaphragm 101 is abnormal is sent ( Step S203).

[Embodiment 2: Example of signal processing using a capacitance other than normal Cx and Cr]
In the capacitance type pressure sensor 100'having the structure shown in FIG. 13, a step portion 116 is provided between the peripheral portion and the central portion of the surface of the diaphragm 101 on the pressure introduction chamber 106 side, and the step portion 116 is used as a boundary. It is divided into a central region (thin region) S1 and a peripheral region (thick region) S2, and the opening is positioned near the step 116 of the diaphragm 101 (peripheral region S2). A plurality of pressure introduction holes 112 are provided in the pedestal plate 107.

FIG. 14 shows the arrangement of the pressure-sensitive fixed electrode 108 and the reference-side fixed electrode 109 formed on the sensor pedestal 105 in the capacitance type pressure sensor 100'in accordance with the positions of the pressure introduction holes 112. In this example, four pressure introduction holes 112 are provided at equal intervals so as to be located between the pressure-sensitive fixed electrode 108 and the reference-side fixed electrode 109. In this case, as shown in FIG. 15, the film 115 is thickly deposited directly under the four pressure introduction holes 112 provided at equal intervals, and the diaphragm 101 is formed in the peripheral region side region as shown in FIG. It is expected that the portion corresponding to the located pressure introduction hole 112 will bend significantly.

Therefore, in the capacitance type pressure sensor 100'with such a structure, as shown in FIG. 17, at a position corresponding to the pressure introduction hole 112 located between the pressure sensitive side electrode pair D1 and the reference side electrode pair D2. , The deposit sensing electrode pair D3 forming the deposit sensing capacity Cd is provided as the third electrode pair.

Then, the ratio ΔCd / ΔCr of the change ΔCd of the accumulation detection capacity Cd at the time of evacuation and the change ΔCr of the reference capacity Cr is calculated as the index β of the abnormality detection, and the calculated index β of the abnormality detection and the index at the time of normal operation are calculated. By comparing with the reference value βref indicating, it is determined whether or not the diaphragm 101 is bent due to a factor other than the pressure.

In the second embodiment, the procedure for reporting an abnormality follows the first embodiment. 18 shows a diagram corresponding to FIG. 10, FIG. 19 shows a diagram corresponding to FIG. 11, and FIG. 20 shows a diagram corresponding to FIG. 12. Also in the first embodiment, it is possible to determine whether or not the diaphragm 101 of the capacitance type pressure sensor 100'is bent due to a factor other than the pressure, but the method of the second embodiment is adopted. Therefore, the sensitivity of abnormality detection can be increased.

In the second embodiment, the ratio of the change ΔCx of the pressure-sensitive capacity Cx and the change ΔCr of the reference capacity Cr at the time of evacuation ΔCx / ΔCr and the ratio of the change ΔCd of the deposition sensing capacity Cd and the change ΔCr of the reference capacity Cr. ΔCd / ΔCr is calculated as the abnormality detection indexes α and β, and an alarm is issued when the abnormality detection index α deviates from the reference value αref ± th or when the abnormality detection index β deviates from the reference βref ± th. You may do so.

[Extension of Embodiment]
Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above embodiments. Various changes that can be understood by those skilled in the art can be made to the structure and details of the present invention within the scope of the technical idea of the present invention.

1 ... Sensor unit, 2 ... Capacity output unit, 3 ... Characteristic measurement unit, 4 ... Reference value storage unit, 5 ... Threshold storage unit, 6 ... Status determination unit, 7 ... Alarm output unit, 100, 100'... Electrostatic capacity Type pressure sensor, 101 ... Diaphragm, 102 ... Diaphragm support, 103 ... Diaphragm component, 104 ... Reference vacuum chamber (cavity), 105 ... Sensor pedestal, 106 ... Pressure introduction chamber, 107 ... Pedestal plate, 108 ... Pressure-sensitive side fixed Electrode, 109 ... Reference side fixed electrode, 110 ... Pressure sensitive side movable electrode, 111 ... Reference side movable electrode, 112 ... Pressure introduction hole, 115 ... Film (deposited film), 200, 200'... Abnormality detection device, Cx ... Pressure sensitive Capacity, Cr ... Reference capacity, Cd ... Accumulation sensing capacity, D1 ... Pressure-sensitive electrode pair, D2 ... Reference side electrode pair, D3 ... Accumulation sensing electrode pair.

Claims (8)

Abnormality of the capacitive pressure sensor that detects abnormalities of the capacitive pressure sensor with multiple electrode pairs whose capacitance between the electrodes changes according to the displacement of the diaphragm that bends according to the pressure of the medium to be measured. It ’s a detection method,
An index calculation step for calculating an abnormality detection index from changes in the capacitances of the plurality of electrode pairs when the test medium is evacuated.
A state determination step for determining whether or not the diaphragm is bent due to a factor other than pressure by comparing the abnormality detection index calculated by the index calculation step with the reference value indicating the index at normal times. , Equipped with
The capacitance type pressure sensor includes first and second electrode pairs as the plurality of electrode pairs.
The first electrode pair forms a pressure-sensitive capacitance Cx in the central portion of the diaphragm.
The second electrode pair forms a reference capacitance Cr on the outer peripheral portion of the diaphragm.
The index calculation step is characterized in that the ratio ΔCx / ΔCr of the change ΔCx of the pressure-sensitive capacity Cx and the change ΔCr of the reference capacity Cr is calculated as the index for detecting the abnormality. Detection method. Abnormality of the capacitive pressure sensor that detects abnormalities of the capacitive pressure sensor with multiple electrode pairs whose capacitance between the electrodes changes according to the displacement of the diaphragm that bends according to the pressure of the medium to be measured. It ’s a detection method,
An index calculation step for calculating an abnormality detection index from changes in the capacitances of the plurality of electrode pairs when the test medium is evacuated.
A state determination step for determining whether or not the diaphragm is bent due to a factor other than pressure by comparing the abnormality detection index calculated by the index calculation step with the reference value indicating the index at normal times. , Equipped with
The capacitance type pressure sensor includes first and second electrode pairs as the plurality of electrode pairs.
The first electrode pair forms a deposition sensing capacity Cd at a position corresponding to the introduction port of the medium to be measured into the diaphragm.
The second electrode pair forms a reference capacitance Cr on the outer peripheral portion of the diaphragm.
The index calculation step is characterized in that the ratio ΔCd / ΔCr of the change ΔCd of the deposition sensing capacity Cd and the change ΔCr of the reference capacity Cr is calculated as the index of the abnormality detection. Detection method. Abnormality of the capacitive pressure sensor that detects abnormalities of the capacitive pressure sensor with multiple electrode pairs whose capacitance between the electrodes changes according to the displacement of the diaphragm that bends according to the pressure of the medium to be measured. It ’s a detection method,
An index calculation step for calculating an abnormality detection index from changes in the capacitances of the plurality of electrode pairs when the test medium is evacuated.
A state determination step for determining whether or not the diaphragm is bent due to a factor other than pressure by comparing the abnormality detection index calculated by the index calculation step with the reference value indicating the index at normal times. , Equipped with
The capacitance type pressure sensor includes first, second and third electrode pairs as the plurality of electrode pairs.
The first electrode pair forms a pressure-sensitive capacitance Cx in the central portion of the diaphragm.
The second electrode pair forms a reference capacitance Cr on the outer peripheral portion of the diaphragm.
The third electrode pair forms a deposition sensing capacity Cd at a position corresponding to the introduction port of the medium to be measured into the diaphragm.
In the index calculation step, the ratio ΔCx / ΔCr of the change ΔCx of the pressure-sensitive capacity Cx and the change ΔCr of the reference capacity Cr and the ratio ΔCd / of the change ΔCd of the deposition sensing capacity Cd and the change ΔCr of the reference capacity Cr. An abnormality detection method for a capacitance type pressure sensor, characterized in that ΔCr is calculated as an index for detecting the abnormality. In the method for detecting an abnormality in a capacitance type pressure sensor according to any one of claims 1 to 3.
A method for detecting an abnormality in a capacitance type pressure sensor, which comprises an alarm output step for outputting an alarm when it is determined by the state determination step that the diaphragm is bent due to a factor other than pressure. In the method for detecting an abnormality in a capacitance type pressure sensor according to any one of claims 1 to 4.
A method for detecting an abnormality in a capacitance type pressure sensor, wherein the base material constituting the capacitance type pressure sensor is sapphire, alumina ceramic, glass, silicon, nickel alloy, or stainless steel. Abnormality of the capacitive pressure sensor that detects abnormalities of the capacitive pressure sensor with multiple electrode pairs whose capacitance between the electrodes changes according to the displacement of the diaphragm that bends according to the pressure of the medium to be measured. It ’s a detector,
An index calculation unit configured to calculate an abnormality detection index from changes in the capacitances of the plurality of electrode pairs when the test medium is evacuated.
By comparing the anomaly detection index calculated by the index calculation unit with the reference value indicating the index at normal times, it is configured to determine whether or not the diaphragm is bent due to a factor other than pressure. a state determination unit was provided with,
The capacitance type pressure sensor includes first and second electrode pairs as the plurality of electrode pairs.
The first electrode pair forms a pressure-sensitive capacitance Cx in the central portion of the diaphragm.
The second electrode pair forms a reference capacitance Cr on the outer peripheral portion of the diaphragm.
The index calculation unit calculates the ratio ΔCx / ΔCr of the change ΔCx of the pressure-sensitive capacity Cx and the change ΔCr of the reference capacity Cr as the index for detecting the abnormality, which is an abnormality of the capacitance type pressure sensor. Detection device. Abnormality of the capacitive pressure sensor that detects abnormalities of the capacitive pressure sensor with multiple electrode pairs whose capacitance between the electrodes changes according to the displacement of the diaphragm that bends according to the pressure of the medium to be measured. It ’s a detector,
An index calculation unit configured to calculate an abnormality detection index from changes in the capacitances of the plurality of electrode pairs when the test medium is evacuated.
By comparing the anomaly detection index calculated by the index calculation unit with the reference value indicating the index at normal times, it is configured to determine whether or not the diaphragm is bent due to a factor other than pressure. Equipped with a state judgment unit
The capacitance type pressure sensor includes first and second electrode pairs as the plurality of electrode pairs.
The first electrode pair forms a deposition sensing capacity Cd at a position corresponding to the introduction port of the medium to be measured into the diaphragm.
The second electrode pair forms a reference capacitance Cr on the outer peripheral portion of the diaphragm.
The index calculation unit calculates the ratio ΔCd / ΔCr of the change ΔCd of the deposition sensing capacity Cd and the change ΔCr of the reference capacity Cr as the index of the abnormality detection.
An abnormality detection device for a capacitive pressure sensor. Abnormality of the capacitive pressure sensor that detects abnormalities of the capacitive pressure sensor with multiple electrode pairs whose capacitance between the electrodes changes according to the displacement of the diaphragm that bends according to the pressure of the medium to be measured. It ’s a detector,
An index calculation unit configured to calculate an abnormality detection index from changes in the capacitances of the plurality of electrode pairs when the test medium is evacuated.
By comparing the anomaly detection index calculated by the index calculation unit with the reference value indicating the index at normal times, it is configured to determine whether or not the diaphragm is bent due to a factor other than pressure. Equipped with a state judgment unit
The capacitance type pressure sensor includes first, second and third electrode pairs as the plurality of electrode pairs.
The first electrode pair forms a pressure-sensitive capacitance Cx in the central portion of the diaphragm.
The second electrode pair forms a reference capacitance Cr on the outer peripheral portion of the diaphragm.
The third electrode pair forms a deposition sensing capacity Cd at a position corresponding to the introduction port of the medium to be measured into the diaphragm.
In the index calculation unit, the ratio ΔCx / ΔCr between the change ΔCx of the pressure-sensitive capacity Cx and the change ΔCr of the reference capacity Cr and the ratio ΔCd / of the change ΔCd of the deposition sensing capacity Cd and the change ΔCr of the reference capacity Cr. Calculate ΔCr as an index for detecting the abnormality.
An abnormality detection device for a capacitive pressure sensor.

Images